U.S. Secretary of the Interior Gail Norton today will propose a ban on the importation of 28 species of the voracious air-breathing, ground-slithering fish known as the snakehead, following the discovery of a thriving school of the creatures in a suburban Maryland pond.

Native to the Yangtze River region of China, the fish has appeared in at least seven states and has upset the natural order by eating virtually everything -- plant and animal -- within its reach.

Maryland officials' discovery of the northern snakehead -- a species that can survive below-freezing temperatures as well as the sweltering days of summer -- alarmed biologists and prompted state officials to convene a posse of experts last week on how best to eradicate the invader.

Federal officials said it appears that the state has a good chance of checking the spread of the fish if none of them has move from the pond into the nearby Little Patuxent River.

"Top predators like this fish are tough to deal with because nothing keeps their numbers down," said Sharon K. Gross, chief of the U.S. Fish and Wildlife Service's invasive species branch. "You're never sure whether they're going to become established and take hold. It's kind of an ecological roulette."

In as little as 60 days, the ban could effectively stop thousands of shipments of fish that are prized by the pet trade for their pugnacious nature and by Asian fish markets for their delicate flesh and ability to live for days out of water.

Under the federal Lacey Act, which Norton will invoke, importation and interstate transportation of the fish would be prohibited in the United States without a special permit.

"These things . . . reproduce quickly. They eat literally anything that's living, including cannibalizing themselves," said Ken Burton, a spokesman for the Interior Department. "They'll eat ducklings. They will eat amphibians. So if you leave them in a body of water for any given time, there'll be nothing left. They're a bad actor."

For aquarium proprietors such as Michael Hresko, manager of House of Tropicals in Glen Burnie, a snakehead ban would cost his store the sale of several hundred fish a year.

Prized by people who like large, aggressive fish, a six-inch snakehead cost about $7 and eventually eat up to $8 worth of goldfish a day.

"There's other fish to sell, different kinds of cichlids that are nasty," Hresko said. "I just worry that they'll ban all large fish."

From 1997 to 2000, more than 16,500 snakeheads of various species legally entered the United States, the Fish and Wildlife Service said. Biologists suspect that pet owners who tired of feeding their snakeheads have been responsible for dumping them in ponds, canals, reservoirs and rivers.

In the Crofton case, the species discovered by a weekend angler is the northern snakehead -- a black, fearsome-looking fish with a gap-toothed maw that is renowned for its appetite for all sorts of fish, from largemouth bass to bluegills.

State investigators learned that two of the fish were ordered from an Asian market by a man who intended to make soup for his ill sister. By the time the fish arrived from New York, however, his sister had recovered and no soup was needed.

Interior Secretary Gale Norton proposed on Tuesday a ban on the importation of 28 species of snakehead, a toothy, torpedo-shaped fish that has been found breeding in a Maryland pond.

In as little as 60 days, the ban could effectively stop thousands of shipments of the fish.

Norton invoked the Lacey Act, which authorizes the secretary to prohibit the importation and interstate transportation of species deemed "injurious, or potentially injurious" to residents, native wildlife or the interests of agriculture or forestry.

On Friday, Maryland officials convened a 12-member panel of scientists, which agreed the state needs to take action against the invasive fish. On Tuesday, the DNR began testing the effectiveness of a fish poison known as rotenone on some of the juveniles at an Eastern Shore laboratory.

Thus far, surveys of nearby waterways have shown no indications that the fish has spread to the Little Patuxent River – just 75 yards away, said DNR Fisheries Director Eric Schwaab.